Environmental Engineering Reference
In-Depth Information
case of Paks NPP, the scope of fatigue calculations is extended to the Safety
Class 1 and 2 piping and components and includes analysis of thermal strat-
ifi cation, too. In regard to its RPV, besides of PTS analysis, the limits and
conditions of safe operation, that is the p-T curve has to be re-analysed in
the frame of revalidation of TLAAs.
The issue of the TLAAs
Review and validation of TLAAs is a rather complex task for the majority
of VVER plants. The issue is related to the availability of design base infor-
mation and incompleteness of the delivered design documentation. Often
only the fi nal results of the analyses are known; in some cases, the analyses
are presumably obsolete. For the majority of VVER plants outside Russia
the TLAAs have to be performed anew using state-of-the-art methods in
accordance with the recent requirements. In comparing the practice of dif-
ferent VVER operating countries, the most complex cases are probably the
Eastern-European VVER-440/213 plants since these plants have to over-
come this issue. For instance, in the case of the Rivne NPP in Ukraine, full
scope stress calculation and fatigue analysis had to be performed for the
VVER-440/213 type units.
The case of Paks NPP Hungary will be discussed below on the basis of
Katona, Rátkai and Pammer (2007), Katona
et al
. (2010) and Katona, Rátkai
and Pammer (2011). TLAAs have to be reviewed and verifi ed for the most
important structures and components (SCs). Developing a methodology
for TLAA reconstitution and defi ning the method of adaptation of ASME
BPVC for a Soviet designed plant has been reported by Katona, Rátkai and
Pammer (2007) and Katona, Rátkai and Pammer (2011). Hungarian regu-
lations require application of state-of-the-art methods and standards in the
time-limiting ageing analyses. ASME Boiler & Pressure Vessel Code, Section
III, edition 2001 (ASME BPVC) had been selected for the reconstitution
of TLAAs and associated strength verifi cation. The code selection requires
understanding of both the Russian (Soviet) design standards and the ASME
BPVC code. Different studies were performed for ensuring the adequacy of
ASME BPVC implementation for VVER-440/213. Calculations were per-
formed for a 50 year extended operational lifetime with an additional margin
of 10 years. The use of ASME BPVC is not a generic approach used by VVER
operators. In some VVER operating countries the conservative PNAE G-7-
002-86 standard is used by the operators and accepted by the regulators.
Mechanical components
To justify the safety of LTO, the scope of TLAAs which must be recon-
structed or newly performed covers Safety Class 1 and 2 mechanical com-
ponents. Examples of the calculations/analyses follow.
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